The invention relates to improvements in transmissions, and more particularly to improvements in continuously or infinitely variable transmissions of the type suitable for use in the power trains of motor vehicles.
A transmission of the type to which the present invention pertains comprises a first adjustable sheave or pulley which can be driven, for example, by the output element (such as the crankshaft or the camshaft) of an internal combustion engine in the power train of an automotive vehicle, a second adjustable sheave or pulley which can transmit torque to a clutch or to a differential in the power train of the vehicle, and at least one endless flexible element (such as a belt or a chain and hereinafter referred to as chain) which is trained over and can transmit torque between the first and second sheaves. As a rule, each sheave comprises a first flange which is rigid (e.g., of one piece) with a shaft, and a second flange which cannot rotate relative to but is movable axially of the shaft. It is also known to provide a transmission of the above outlined character with at least two plenum chambers which can receive a pressurized fluid from a suitable source, and with an annular sealing device (such as a sealing ring) which can serve to establish or to interrupt the flow of fluid between the chambers.
A transmission of the above outlined character is disclosed, for example, in published German patent application Serial No. 195 44 644. Such transmissions can employ a lip seal which can prevent the flow of fluid between two chambers when the pressure of fluid in one of the chambers is higher than that of the fluid in the other chamber but which is expected to permit the fluid to flow from the other chamber into the one chamber when the pressure of fluid is higher in the other chamber.
A drawback of such standard sealing devices is that a lip seal is likely to be shifted and/or tilted and/or otherwise deformed and/or displaced so that it is incapable of reliably permitting the flow of a fluid (such as oil) from one of the plural chambers into the other chamber or chambers when such flow is desirable or necessary for proper operation or functioning of the transmission.